This is a National stage application of PCT/JP96/00834, filed Mar. 29, 1996.
The present invention relates to a porous carbonaceous material which has micropore and/or sub-micropore structures which are suitable for the adsorption of small molecules such as nitrogen and oxygen, and to a manufacturing method therefor. In addition, the present invention provides a porous carbonaceous material which can be used in applications such as an adsorbing agent for use in separating and refining industrially used gases, and as a material for electrodes of a secondary battery.
As starting materials for carbonaceous materials, carbonized plant and animal material such as lignite, brown coal, anthracite coal, coke, wood charcoal, coconut shell char; any kind of resin such as phenol resin, furan resin, vinylidene chloride copolymer, etc. which have been heat-treated (carbonized) in an atmosphere of inert gas; and the like can be used. In the present invention, these starting materials are called generic carbon compounds, and materials obtained by carbonization of carbon compounds are called carbonized charcoal.
Because carbonaceous materials are chemically inactive, they are used in a wide range of applications such as adsorption agents, catalysts, electrode materials, structural materials for use in machines, etc.; however, these applications are closely related to the structure of the carbon.
That carbon which is referred to as porous carbon has special effects due to the development of pores. For example, using the adsorption phenomena, there are mixture separation and refining actions. In addition, the carbon used in electrical double layer capacitors, the carbon used in lithium secondary batteries, and the like display electrochemical storage effects.
The structure of the carbonaceous material can take various forms depending on the starting material, and the manufacturing method.
Char and activated carbon obtained by activating char comprise microcrystalline carbon (crystallite), and carbon which takes on a chain structure. When the carbonaceous material is a nongraphitizing carbon, the crystallites take on a structure which is layered in a disorderly manner, and a wide range of pores, from micropores to macropores, are formed in the gaps between these crystallites.
The crystallites are layers of net planes of six membered carbon rings of several parallel layers, and graphite carbon which has a six membered carbon ring structure bonds using hybridized orbitals SP2. A net plane comprising six membered ring carbon is called a basic plane.
A graphitizing carbon grows/develops crystallites by means of heating at a high temperature, and finally becomes graphite.
A nongraphitizing carbon and a graphitizing carbon which has not been completely graphitized usually contain unorganized carbon. Unorganized carbon is carbon other than graphite carbon which is chemically bonded to graphite carbon only; carbon which has a chain structure; carbon which is stuck around six membered ring carbon; carbon which is in the periphery (the prism plane) of six membered ring carbon; carbon which is held in cross-linked structures with other six membered carbon rings (crystallites), and the like. Unorganized carbon is bonded with oxygen atoms, hydrogen atoms, and the like in forms such as Cxe2x80x94H, Cxe2x80x94OH, Cxe2x80x94OOH, and Cxe2x95x90O; or is in the form of double bonded carbon (xe2x80x94Cxe2x95x90Cxe2x80x94).
When pores have a diameter of 0.8 nm or less, they are called sub-micropores, when they have a diameter in the range of 0.8xcx9c2 nm, they are called micropores. Pore diameters within these spheres are approximately of the same order as the diameter of adsorbed molecules, and therefore these pores are believed to take part in the adsorption phenomena.
Because present measuring techniques are unable to directly observe the pore structure of pores in the sub-micropore range, the situation at present is such that it is not possible to establish this as a general theory.
It is believed that the quantity of small molecules, such as nitrogen and oxygen, adsorbed is correlated with the degree of development of micropores and/or sub-micropores, and that the extent of the quantity of small molecules, such as nitrogen and oxygen, adsorbed indicates the degree of development of micropores and/or sub-micropores.
Methods for manufacturing porous carbonaceous material have variously been offered. In the following, representative manufacturing methods will be explained.
As commonly used methods for obtaining porous carbonaceous material, methods are known in which activation treatments are given in oxidizing gases such as steam, carbon dioxide, and air.
In activation treatments, the oxidation/corrosion (the carbon is gasified) of carbon occurs by means of an activating agent. In other words, new pores are formed in the surface of the carbonaceous material, and, in addition, open pores are made even larger. As a result, it is believed that the specific surface area and the pore volume are increased. However, in normal activation treatments, the activation yield (the carbon yield in other treatments) is of the level of 40xcx9c80%, and the carbon loss reaches 20xcx9c60%. In addition, it is not possible to form pores of a uniform pore diameter.
Here, the activation yield and the carbon yield take the weight of carbon compounds before treatment as 100, and express the weight after treatment.
As an example of steam activation, there is Japanese Patent Application, First Publication, No. Hei 1-242409; as an example of carbon dioxide activation, there is Japanese Patent Application, First Publication, No. Hei 5-132377; as a combination method of air (oxygen) activation with steam and/or carbon dioxide activation, there is Japanese Patent Application, Second Publication, No. Hei 5-49606; and in addition, as an example of activation by means of hydroxides of sodium, potassium, and the like, there is Japanese Patent Application, First Publication, No. Hei 2-97414 (Japanese Patent Application, Second Publication, No. Hei 5-82324).
Methods of manufacturing porous carbonaceous material by means of carbonization of polymeric resins which have specific molecular structures are also known. When decomposing organic substances by carbonization, the carbon re-bonds in such a way as to form an aromatic structure of a six membered ring which is thermally stable. The proportion of components other than carbon contained within the resin starting material is still not clear.
As examples of the carbonization of polymeric resins, there are Japanese Patent Application, Second Publication, No. Sho 60-20322, Japanese Patent Application, First Publication, No. Hei 6-187972, U.S. Pat. No. 4,839,331, U.S. Pat. No. 3,960,768, and the like.
The above-mentioned U.S. Pat. No. 4,839,331 and U.S. Pat. No. 3,960,768 aim to reform the carbonaceous material by reacting sulfur compounds and halogens with polymeric resins beforehand. The present invention aims to reform the carbonaceous material by means of reacting a post-carbonization material (carbonized charcoal) with chlorine.
As a manufacturing method which obtains porous carbonaceous material without making use of an activation treatment, there is Japanese Patent Application, First Publication, No. Hei 4-310209. This application discloses a way of obtaining an adsorption agent with oxygen selectivity by means of heating coconut shell char, which has been crushed into granules, in an inert gas at 775 up to 900xc2x0 C. while controlling the heating speed, and maintaining this for 8 hours.
Japanese Patent Application, First Publication, No. Sho 62-108722 discloses a method of forming pores in carbonaceous material by mixing organic metal compounds into a heated polymeric resin, heat treating this mixture, and eluting the contained metals.
A number of examples of oxygen and nitrogen adsorption amounts for carbonaceous materials (activated carbon) manufactured by conventional techniques are shown in Table 1. This data was recorded in chemical references and patent references, in addition to the quantities adsorbed (xe2x80x9cLiterature Valuesxe2x80x9d in the Table) at equivalent adsorption temperature lines in the literature, Henry type adsorption is presumed and values calculated for 1 atm (Values Calculated for 1 atm in the Table) are also shown in the table. Moreover, there are cases where the measurement temperature is unclear, and these measurement temperatures are presumed to be temperatures close to room temperature.
Note: In the above xe2x80x9cLiterature Valuexe2x80x9d Column, the xe2x80x9c?xe2x80x9d indicates that the measurement temperature is not clearly recorded. In the xe2x80x9cConverted Value for 1 atmxe2x80x9d Column, ccSTP/g is a value calculated for the gas of volume cc adsorbed for 1 g at conditions of standard temperature (0xc2x0 C.) and pressure (1 atm).
From the above publicly known literature, the largest amount of nitrogen adsorbed is 8.94 ccSTP/g (calculated to be 9.76 cc/g at 25xc2x0 C. and 1 atm), the largest amount of oxygen adsorbed is 12.2 cc/g, and carbonaceous material which has adsorption quantities greater than these are not known.
Moreover, oxygen from carbonaceous material which has no particular allowance for oxygen selectivity have some differences with the amount of nitrogen adsorbed, but it is clear for Table 1, references 3, 4, and 6, that the values are approximately the same.
The following examples give data for carbon dioxide adsorption by activated carbon. 1) Kawazoe et al. Production Research, Vol. 25, No. 11, page 513, 1973 [8.5 g/100 g=43 mlSTP/g (20xc2x0 C., 1 atm)]. 2) Yano et al. Kagaku Kogaku, Vol. 25, No. 9, page 654, 1961 [30 ccSTP/g (30xc2x0 C., 1 atm)]. 3) Kagaku Kogaku Handbook, page 589, 1992 [40 cm3 NTP/g (37.7xc2x0 C., 1 atm)].
The following examples give data for methane adsorption by activated carbon. 1) Nitta et al. J. Chem. Eng. Jpn, Vol. 25, No. 2, page 176, 1992 [1 mol/kg=22.4 mlSTP/g (25xc2x0 C., 1 atm)]. 2) Kimberly et al. Chem. Eng. Science, Vol. 47, No. 7, page 1569, 1992 [0.7xcx9c1.1 mmol/g=15.7xcx9c24.6 mlSTP/g (25xc2x0 C., 1 atm)]. 3) Kagaku Kogaku Handbook, page 589, 1992 [21 cm3 NTP/g (37.7xc2x0 C., 1 atm)].
The specific surface area for normal activated carbon is of the level of 700xcx9c2000 m2/g (Kagaku Kogaku Handbook, 1992), and with regard to the pore volume for normal activated carbon, for example, the pore volume of micropores to sub-micropores is of the level of 0.2832xcx9c0.4365 ml/g, and pore volume for diameters to 20 nm is of the level of 0.4408xcx9c0.6938 ml/g (Shinban Kasseitan (Activated Carbon, New Edition) 1995).
The composition ratio (the H/C atomic ratio) of hydrogen to carbon in carbonaceous material can vary widely depending on the temperature of carbonization, but, for example, when phenol is carbonized at 400xcx9c740xc2x0 C., it is 0.55xcx9c0.07 (Japanese Patent Application, First Publication, No. Sho 60-170163).
The way that these parameters are concerned with adsorption quantities and electrochemical energy storage capacity is not sufficiently clear.
As indicators which show the characteristics of crystallites, examples which are disclosed in the literature of survey values for the distance of the (002) measured by means of X-ray diffraction are as shown in Table 2; sizes of between 0.3367 and 0.395 nm are known.
Electrodes for electrical double layer capacitors are called polarizable electrodes, but those which have much larger electrostatic capacity are being demanded. Since electrical capacity (electrostatic capacity) which is stored in electrical double layers is in general terms determined by the surface area of the solid liquid interface, as electrode materials, carbonaceous materials which have large specific surface areas and have conductivity are used. In particular, activated carbon which has been given an activation treatment is often used.
As conventional techniques for carbon electrodes for use in electrical double layer capacitors, U.S. Pat. No. 3,700,975, Japanese Patent Application, Second Publication, No. Hei 4-70770, Japanese Patent Application, Second Publication, No. Sho 63-10574, Japanese Patent Application, First Publication, No. Hei 4-175277, Japanese Patent Application, First Publication, No. Hei 1-321620, and the like are known.
In conventional manufacturing methods for porous carbonaceous material, because the micropores and/or sub-micropores are not sufficiently developed, when used as an adsorbing agent directed to gases which have small molecular diameters such as nitrogen, the adsorption capacity is insufficient. In addition, there is the problem that the carbon yield is low.
In addition, even when used as an electrode material such as carbon for use in electrical double layer capacitors and carbon for use in lithium secondary batteries, the storage capacity for electrochemical energy is insufficient.
The present invention solves these problems.
In order to solve the above-mentioned problems, the inventors of the present invention earnestly researched manufacturing methods for porous carbonaceous material. As a result of this, they discovered that when carbonized charcoal is given chlorine treatment, the amount of nitrogen adsorbed is increased significantly, and they realized the accomplishment of the present invention.
Moreover, in the following description, the present invention is explained chiefly using chlorine gas as an example; however, using the same technical concept, halogens such as bromine can also be used.
The manufacturing method for the porous carbonaceous material of the present invention is characterized by halogen treatment of carbonized charcoal. In FIG. 1, a process diagram of a manufacturing method of a porous carbonaceous material by means of a halogen treatment according to the present invention is shown. The halogen treatment of the present invention is a treatment which provides a halogenation step in which a halogenation treatment is conducted which obtains halogenated carbonized charcoal by bringing carbonized charcoal into contact with halogen gas; and a dehalogenation step in which a dehalogenation treatment is conducted which eliminates part or all of the halogen atoms in the subsequently halogenated carbonized charcoal. According to the present invention, as the above-mentioned halogen, chlorine or bromine can be suitably used.
Using chlorine as an example, the degree of chlorination of chlorinated carbonized charcoal is expressed by the atomic ratio of chlorine and carbon (Cl/C). This atomic ratio in the chlorination step is a molar ratio of the numbers of atoms which are obtained by the conversion from the weight of carbon and the weight of chlorine, in which the weight of the carbonized charcoal before the chlorination step is assumed to be the weight of carbon and the weight increase due to the chlorination step is assumed to be the weight of chlorine. In addition, in the dechlorination step, the degree of dechlorination is calculated from the value which is obtained by taking the weight decrease due to the dechlorination step to be the reduction in the quantity of chlorine, converting this into the number of atoms, and subtracting it from the number of chlorine atoms in the chlorinated carbon.
In real chlorine treatments, due to the destructive distillation action accompanying the progress of carbonization, the activated action by steam (the gasification of carbon) and the like, the ratio of the number of atoms according to the above definition can be a negative value.
The chlorination step is characterized by conducting a heat treatment on the carbonized charcoal in chlorine gas which has been diluted with an inert gas such as nitrogen at a temperature of 350xcx9c1000xc2x0 C., and preferably of 400xcx9c700xc2x0 C.
When the temperature of the heat treatment of the chlorination step exceeds 1000xc2x0 C., due to the reduction in the quantity of hydrogen atoms as the destructive distillation progresses, the degree of chlorination (Cl/C) is reduced, and this is not desirable. In addition, since it is necessary that the carbons of the polyaromatic ring structures be inactive with respect to the chlorine, it is preferable that the temperature of the chlorination step be 1000xc2x0 C. or less. In addition, when the temperature of the heat treatment of the chlorination step is less than 350xc2x0 C., because the reaction speed of the unorganized carbon and the chlorine is too slow, a long period of time is required for the chlorination step, and this is not desirable.
With regard to the supply rate for the chlorine gas, when the concentration of the chlorine gas is 10% by volume, the superficial velocity in the column is of the level of 0.2xcx9c0.3L/(minxc2x7cm2). The time for the chlorination treatment is about 30 minutes when in the high temperature region of the above-mentioned temperature range; however, about 120 minutes are required when in the low temperature range close to 400xc2x0 C. Moreover, the flow rate of the gas is expressed by the volume (L) of the gas at room temperature at approximately atmospheric pressure per period of time (minutes) (this is the same hereinafter).
Here, the inert gas is nitrogen, or rare gases such as helium, argon, and the like, or a mixture of these gases.
By means of the above-mentioned chlorination treatment, a chlorinated carbonized charcoal is obtained which has an atomic ratio of chlorine to carbon (Cl/C) of preferably 0.03 or greater, and more preferably of 0.07 or greater. Moreover, when this atomic ratio is less than 0.03, the contribution to the formation of the micropores is small, therefore this is not desirable.
In addition, the upper limit of the above-mentioned atomic ratio is determined by the carbonization temperature and the quantity of hydrogen atoms in the carbonized charcoal; however, it is understood from the Examples mentioned below that the desired results of the present invention can be obtained at 0.315 or less.
In a bromination treatment, even when the atomic ratio of bromine to carbon (Br/C) approaches 0.01, the effects of the present invention can be obtained.
The dechlorination step is characterized by being conducted by means of a high temperature dechlorination treatment, a low temperature dechlorination treatment, or a treatment which combines a high temperature dechlorination treatment and a low temperature dechlorination treatment.
The degree of dechlorination is preferably a situation in which the above-mentioned atomic ratio after the dechlorination step is 0.02 or less; however, it is not absolutely essential for complete dechlorination.
The high temperature dechlorination treatment is characterized by a heat treatment conducted at a temperature of 600xcx9c1300xc2x0 C. under vacuum evacuation or in an inert gas, or preferably at 900xcx9c1100xc2x0 C. when the carbonaceous material is to be used as an adsorbent, or 600xcx9c900xc2x0 C. when it is to be used as electrode material. The degree of vacuum evacuation is not particularly limited, a vacuum of vacuum evacuation approaching 10 Torr is sufficient. A time of 20 xcx9c30 minutes is sufficient for the heat treatment.
When a high temperature dechlorination treatment conducted in inert gas is conducted at treatment temperatures exceeding 1300xc2x0 C., the openings of the fine pores become too small due to heat shrinkage and nitrogen gas cannot enter inside the fine pores, therefore, the desired amount of nitrogen adsorption cannot be obtained. In addition, when a high temperature dechlorination treatment conducted in inert gas is conducted at treatment temperatures lower than 600xc2x0 C., sufficient dechlorination cannot take place.
Moreover, in the high temperature dechlorination treatment, the chlorine in the carbonized charcoal is not completely dechlorinated, and a part of the chlorine remains.
The low temperature dechlorination treatment is characterized by a heat treatment conducted at a temperature of 600xcx9c850xc2x0 C., and preferably at 650xcx9c750xc2x0 C., in a gas of a hydrogen containing compound or a gas of a hydrogen containing compound; which has been diluted with inert gas. A time of 20xcx9c30 minutes is sufficient for the heat treatment.
In the low temperature dechlorination treatment, the chlorine in the carbonized charcoal is almost completely dechlorinated.
Here, the gas of a hydrogen containing compound; is steam (H2O); hydrogen; lower hydrocarbons, such as methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), butane (C4H10), and butylene (C4H8); and mixtures of these gases. As a gas of a hydrogen containing compound; in an inert gas, the exhaust gas of LPG (liquid petroleum gas) which has been incompletely burned is suitable for industrial use. The composition of the above-mentioned exhaust gas is, for example, steam: 13xcx9c17% by volume; carbon dioxide: 9xcx9c12% by volume; carbon monoxide: 0.01xcx9c1% by volume; nitrogen: 68xcx9c74% by volume; and unburned lower hydrocarbons: 0.01xcx9c3% by volume.
When the above-mentioned gas of a hydrogen containing compound; is steam, the concentration of the steam is not particularly limited; however, when the superficial velocity in the column is from 0.05 to 0.15 L/(minxc2x7cm2), 3% by volume is sufficient.
Furthermore, when the above-mentioned gas of a hydrogen containing compound; is steam, and the heat treatment occurs at a temperature exceeding 850xc2x0 C., the activation activity due to the steam progresses too far, thereby obstructing the formation of micropores, and in addition to reducing the carbon yield, the effects of the present invention are reduced.
When the above-mentioned gas of a hydrogen containing compound; is hydrogen, since there is no activation activity, there is no restriction on the above-mentioned upper limited.
When the above-mentioned gas of a hydrogen containing compound; is a lower hydrocarbon such as methane, the concentration of the lower hydrocarbon is not particularly limited; however, when the gas column speed is 0.05xcx9c0.15 L/(minxc2x7cm2), 20% by volume is sufficient.
Furthermore, when the above-mentioned gas of a hydrogen containing compound; is a lower hydrocarbon, and the heat treatment occurs at a temperature exceeding 850xc2x0 C., a carbon impregnation effect due to the thermal decomposition of the lower hydrocarbon is produced, and because the micropores are blocked, the effects of the present invention are reduced.
When the above-mentioned gas of a hydrogen containing compound; is either steam or a lower hydrocarbon, and the heat treatment occurs at a temperature of less than 600xc2x0 C., sufficient dechlorination can not take place.
There are five treatment methods for dechlorination: methods in which only a high temperature dechlorination treatment is conducted; methods in which only a low temperature dechlorination treatment is conducted; methods which are combinations of these methods in which a high temperature dechlorination treatment and a low temperature dechlorination treatment are successively conducted; methods in which a low temperature dechlorination treatment and a high temperature dechlorination treatment are successively conducted; and methods in which a high temperature dechlorination treatment, a low temperature dechlorination treatment, and a high temperature dechlorination treatment are successively conducted. These are shown in Table 3.
Within the treatment methods for dechlorination explained above, when a treatment in which a high temperature dechlorination treatment and a low temperature dechlorination treatment are successively conducted is adopted using a gas of a hydrogen containing compound; steam, or a mixture of steam and a lower hydrocarbon, the effects of the present invention become even more apparent.
In the manufacturing method of the above-mentioned porous carbonaceous material, various carbonized charcoals can be used, but, in particular, carbonized charcoal obtained by the carbonization of coconut shell, phenol resin, furan resin, or vinylidene chloride resin are the most suitable as starting materials.
When the chlorine content relative to carbon after the dechlorination treatment is 17.7% by weight or less (chemical analysis value), in other words, an atom ratio of chlorine relative to carbon of 0.06 or less, the effects of the dechlorination treatment of the present invention are apparent.
By means of conducting the above-mentioned manufacturing method using the above-mentioned carbonized charcoals as a starting materials, a porous carbonaceous material is obtained for which the amount of nitrogen adsorption at 25xc2x0 C. and 1 atm is 12.5xcx9c20 cc/g. This amount of nitrogen adsorption is 15xcx9c50% greater than conventional carbonaceous materials.
According to the manufacturing method for the porous carbonaceous material of the present invention, a porous carbonaceous material is obtained which has a pore volume calculated from benzene adsorption of 0.20xcx9c0.50 cm3/g, and a specific surface area of 600xcx9c1300 m2/g. On the other hand, carbonaceous material which has been given the activation treatment of the conventional art has a pore volume calculated by benzene adsorption of the size of 0.25xcx9c0.7 cm3/g, a specific surface area of 800xcx9c1900 m2/g, and nitrogen adsorption of about 10xcx9c12 cc/g.
The amount of nitrogen adsorbed by a chlorine treated carbonaceous material is extremely large when compared with that of carbonaceous material which has been given the activation treatment of the conventional art, and even when their pore volume and specific surface area are approximately the same size. The chlorine treated carbonaceous material has a large number of micropores and/or sub-micropores suitable for the adsorption of small molecules such as nitrogen, this is so even though the amount of benzene, which has a large molecular diameter, adsorbed is approximately the same compared with that of carbonaceous material which has been given the activated treatment of the conventional art.
By means of the manufacturing method for the porous carbonaceous material of the present invention, a carbonaceous material is obtained in which the amount of carbon dioxide adsorbed at 25xc2x0 C. and 1 atm is 60xcx9c90 cc/g. Compared with carbonaceous materials obtained by normal methods, the amount of carbon dioxide adsorbed is approximately 20xcx9c79% greater.
By means of the manufacturing method for the porous carbonaceous material of the present invention, a carbonaceous material is obtained in which the amount of methane adsorbed at 25xc2x0 C. and 1 atm is 25xcx9c33 cc/g. Compared with carbonaceous material obtained by normal methods, the amount of methane adsorbed is approximately 14xcx9c51% greater.
According to the manufacturing method for porous carbonaceous material of the present inventions, a carbonaceous material is obtained in which the distance of the (002) is 0.40xcx9c0.43 nm.
According to the manufacturing method for the porous carbonaceous material of the present invention, a carbonaceous material is obtained in which, according to X-ray photoelectron spectroscopy, the carbons of the polyaromtic ring structures are 66xcx9c74% of the total carbon.
According to the manufacturing method for porous carbonaceous material of the present invention, a carbonaceous material is obtained in which the volume of accumulated pores with a radius of 1.5 nm or less is 90% or greater with regard to the volume of all pores.
According to the manufacturing method for porous carbonaceous material of the present invention, a carbonaceous material is obtained which has a true density of 1.75xcx9c1.90 cm3/g.
According to the manufacturing method for porous carbonaceous material of the present invention, a carbonaceous material is obtained in which the atomic ratio is 0.010xcx9c0.17, and the weight ratio is 0.084xcx9c1.42% by weight for hydrogen to carbon.
According to the manufacturing method for porous carbonaceous material of the present invention, a carbonaceous material in which the value of indicator G, which shows the degree of crystallinity, is 1.2xcx9c1.5 according to Raman spectroscopy.
According to the manufacturing method for porous carbonaceous material of the present invention, a carbonaceous material is obtained in which electric conductivity is 30xcx9c100 S/cm at room temperature.
By means of using the carbonaceous material obtained by means of the manufacturing method for porous carbonaceous material of the present invention, an electrical double layer capacitor is obtained in which capacitance is 70xcx9c90 F/cm3.
In addition, according to the manufacturing method for porous carbonaceous material of the present invention, the porous carbonaceous material can be manufactured at a high yield.
Another invention of this application relates to an activation method for carbonaceous material. That is, by means of this activation method, after obtaining chlorinated carbonized charcoal by bringing carbonized charcoal into contact with chlorine gas, it is possible to selectively gasify the carbon atoms which are combined with the chlorine atoms (the chlorinated carbon) alone by means of conducting a heat treatment on the chlorinated carbonized charcoal in steam or steam which has been diluted with inert gas at 500xcx9c800xc2x0 C.
Next the action of the means of the present invention will be explained.
There are a number of structural models for nongraphitizing carbon and graphitizing carbon in which the degree of crystallinity is insufficient. In the Franklin Model (Otani and Sanada, xe2x80x9cThe Basics of Carbonization Engineeringxe2x80x9d, page 13, Ohm Company, 1980; Hagiwara xe2x80x9cRevised Guide to Carbon Materialxe2x80x9d, page 188, Carbon Materials Society, 1984), which has been known for a long time, microcrystal (crystallites) comprising multiple layers of a net plane of six-membered carbon rings take a structure like piled up building blocks. With regard to low temperature treated char, there is also a model in which building blocks are constructed by single layer carbon net planes (Yokono xe2x80x9cCarbonxe2x80x9d, No. 133, page 115, (1988)). In addition, there is also a model in which it is as if the carbon net plane is lined up on plane shavings (H. F. Stoeckli, xe2x80x9cCarbonxe2x80x9d 28, page 1, (1990)).
When chlorine gas is brought into contact with carbonized charcoal, the chlorine is physically adsorbed and/or chemically adsorbed to the carbonized charcoal. When the contact temperature is increased, the amount of physical adsorption is reduced and the amount of chemical adsorption is increased. In the main, chemical adsorption occurs by reaction with the above-mentioned unorganized carbon. Since the present invention makes use of the reaction of chlorine with unorganized carbon, it is necessary that the carbonized charcoal used in the present invention be nongraphitizing carbon and graphitizing carbon in which the degree of crystallinity is insufficient.
Unorganized carbon which has been reacted with chlorine can be considered to take chemical structures such as Cxe2x80x94Cl, Cxe2x80x94Oxe2x80x94Cl, Cxe2x80x94Oxe2x80x94Oxe2x80x94Cl, C(xe2x95x90O)xe2x80x94Oxe2x80x94Cl, and Cxe2x95x90Cl2.
When hydrogen atoms are bonded to unorganized carbon, the chlorination reaction shown in Formula (1), Formula (2), and Formula (3) occurs (C| shows unorganized carbon; a pair of symbols C| which are shown in a vertical alignment are unorganized carbons which are. next to each other in the same net plane or crystallite). 
Formula (1) is a chlorine addition reaction for double bonded carbon, Formula (2) and Formula (3) are exchange reactions of chlorine atoms with hydrogen atoms which are bonded to unorganized carbon (hydrogen chloride in a molar equivalent to chlorine is generated), and Formula 4 is a dechlorination reaction (hydrogen chloride twice that of the chlorine is generated). It is presumed that these four reactions all occur.
As is clear from the above-mentioned reactions, the larger value for the above-mentioned atomic ratio (Cl/C) is determined by the proportion of unorganized carbon in relation to total carbon atoms. The amount of unorganized carbon (therefore, hydrogen atoms, oxygen atoms, double bonded carbon, etc.) is dependent on the degree of carbonization in the carbonized charcoal.
When the dechlorination treatment occurs in an inert gas, the chlorine which is bonded to the unorganized carbon is eliminated as hydrogen chloride (HCl) by means of the reactions shown in Formula 5 and Formula 6.
C|xe2x80x94Cl+C|xe2x80x94Hxe2x86x92C|xe2x80x94C|+HClxe2x80x83xe2x80x83(5)
C|xe2x80x94Cl+C|xe2x80x94Hxe2x86x92Cxe2x95x90C|+HClxe2x80x83xe2x80x83(6)
When the dechlorination treatment takes place in a gas of a hydrogen containing compound; the chlorinated carbon is reduced by the hydrogen containing as shown in Formula (7) and Formula (8).
C|xe2x80x94Cl+C|xe2x80x94Cl+2Rxe2x80x94Hxe2x86x92C|xe2x80x94C|+2HCl+2Rxe2x80x2xe2x80x83xe2x80x83(7)
xe2x80x83C|xe2x80x94Cl+Rxe2x80x94Hxe2x86x92C|xe2x80x94H+HCl+Rxe2x80x2xe2x80x83xe2x80x83(8)
Here, Rxe2x80x94H represents a hydrogen containing compound, and Rxe2x80x2 represents an oxide of Rxe2x80x94H.
By means of the reactions of Formula (5), Formula (6), and Formula (7), new bonds between carbon atoms (hereinafter, carbon bonds) are generated. The formation of these new carbon bonds can be considered to achieve actions such as the action of repairing defects in the polyaromatic ring structure of the crystallites or the carbon net planes, the action of growth (change in form) of the crystallites or the carbon net planes, and the action of changes in the condition of crystallite to crystallite bonds (change of the aggregation condition). At this time, it can also be considered that the effect of heat shrinkage due to heating has a synergistic action.
In whichever way, by means of newly formed carbon bonds, it is presumed that the sub-micropores and/or the micropores which surround the crystallites are in a plurality of shapes.
When carbon which is in a position in which the carbon bonds cannot participate is chlorinated, hydrogen atoms are again added in accordance with Formula (8). In other words, all carbon which is chlorinated does not contribute to the generation of the above-mentioned carbon bonds.
As shown in the Examples, when the hydrogen containing compound is a lower hydrocarbon such as methane, the weight after dechlorination is not reduced even if dechlorination and rechlorination are repeated. In other words, as shown in Formula 9 below, there is no activating effect.
However, when dechlorination and rechlorination are repeated in steam, as shown in Formula (9), the average weight reduction for each cycle of dechlorination and rechlorination is approximately equal to the weight reduction when chlorinated carbon is gasified.
Consequently, when the hydrogen containing compound gas is steam, in addition to the reduction action of Formula (8), Formula (7), and (R=OH), an effect in which chlorinated carbon is selectively activated also occurs as shown in Formula (9) (n is 1 or 2).
Cxe2x80x94Cxe2x80x94Cl+H2Oxe2x86x92Cxe2x80x94H+COn+HClxe2x80x83xe2x80x83(9)
As explained above, according to the reaction of each of the above-mentioned Formula (7), Formula (8), and Formula (9), when a hydrogen containing compound is added in a dechlorination step, it is possible to promote dechlorination.
The mechanism of dechlorination is complicated, and reactions other than those of the above-mentioned Formulae (5) to (9) can be considered.
The generation means for micro pores and/or sub-micro pores according to the above-mentioned chlorination treatment is a means which is completely different to conventional generation means which depend on activated treatments and the like, and loss of carbon (gasification) is small.
In dechlorination treated carbonaceous material, even when a part of the chlorine bonded to the carbon atoms remains, there are the above-mentioned uses and effects.
When a chlorination treatment is carried out, hydrogen can be replaced by chlorine. The bond dissociation energy with regard to carbon is smaller for chlorine when compared with hydrogen. As a result, chlorine is more easily dissociated compared with hydrogen, and carbon atoms can be considered as being easily taken into the carbon net plane structure by means of reduction and the like. In addition, it is presumed that for the same reason, crystals which have few defects are produced, and this is considered to be the cause of the manifested high adsorption strength.
The bond dissociation energy for bromine is smaller than that for chlorine. For this reason, for bromine, crystallization progresses even more easily, crystals with few defects are produced, and it is assumed that uses and effects will be manifested which are the same as those for chlorine.
Porous carbonaceous material is an aggregate of graphite microcrystallites. As a basic indicator which shows the characteristics of the crystallites, it is possible to consider the distance of the (002) calculated from X-ray diffraction measurements. As indicators showing the characteristics in order to understand the crystallites as a whole, the proportion of carbons of the polyaromatic ring structures, obtained by means of X-ray photoelectron spectroscopy; the G value showing the condition of crystallization, obtained by Raman spectroscopic measurement; the proportion of carbon and hydrogen contained in the carbonaceous material; and the real density of carbonaceous material can be considered. It can be considered that, by virtue of these characteristics, the properties desired for an electrical double layer capacitor or the property of electrical conductivity are given to a carbonaceous material. In addition, by virtue of the characteristics of pore volume and the specific surface area of the pores which are formed by the crystallites or the their aggregation conditions, the properties of gas adsorption are given.